Skip to content

Minimising nitrogen fertiliser requirements with legumes

By Cameron Leckie, SQNNSW Innovation Hub Regional Soil Coordinator
14 April 2026

Nitrogen is one of the most essential plant macronutrients, required in large amounts to maximise plant growth. It is essential for a range of plant process from building amino acids and proteins, to driving photosynthesis and ultimately determining yield.

The fertilisers Australian farmers apply each year contains 1.6 million tonnes of nitrogen, two-thirds of which is applied as urea; Australia uses, on average, 3.5–4 million tonnes of urea each year.

Prior to the war in West Asia, Australia typically sourced nearly 70% of its urea from the Persian Gulf.

The result: Australia is likely to face both urea shortages and high prices this year. Timing is another problematic issue with peak imports typically arriving between April and June for winter cropping.

There is a urea plant under construction in Karratha Western Australia that is scheduled for commissioning in 2027. It is expected to produce more than half of Australia’s urea requirements. Whilst this should enhance security of supply, it is unlikely to address cost pressures. Urea, as a globally traded commodity, is priced on international benchmarks, as are natural gas, wheat and many other commodities.

With the end result of the war unknown, including how long it lasts and how much damage is caused to oil, gas and petrochemical infrastructure, the safe assumption is that we will face structurally higher prices for key inputs into Australian agriculture including nitrogen fertiliser over the medium term.

If this is the case, what other options are there?

A recently published major global review (Peoples et al., 2026) and associated Grains Research and Development Corporation update examined the integration of legumes to enhance cereal production with a focus on wheat. The review was led by several Australian scientists and had several aims including identifying the different uses of legumes, the role they play in Biological Nitrogen Fixation (BNF) and their impact on cereal grain yield, biomass production and nitrogen uptake. The review offers insights that may be useful for Australian growers and their advisors to manage the unexpected circumstances we now find ourselves in.

Legumes are important because not only can they access soil mineral nitrogen, but they also fix atmospheric nitrogen via symbiotic relationships with the soil bacteria rhizobia. Some important findings of the 2026 paper:

  • On average, legumes fix the equivalent of 90kg of nitrogen for every ton of grain that is harvested. For chickpea, assuming a yield of 2 tonnes per hectare, that equates to 180kg per hectare of nitrogen fixation.
  • Average yield improvements of the first wheat crop after pulses (compared to wheat grown after a previous unfertilised wheat, barley or canola crop) averaged +0.67 t/ha.
  • Although there is less data (and hence certainty) the nitrogen uptake benefits observed in the first wheat crop appeared to be greater after forage legumes and green/brown manure crops.
  • The effect of previous pulse crops generally carries over to a second season, albeit with less effect. For forage legumes evidence suggests that the effect may carry over for up to three seasons.
  • Other positive non-nitrogen related effects from legumes could include improved availability of other plant nutrients, improved soil structure, declines in cereal crop disease inoculum leading to more rigorous and healthier wheat roots, and an expansion of weed management options.

The overall conclusion from the review is that the increased incorporation of legumes into wheat cropping systems could provide opportunities to reduce nitrogen fertiliser. Without jeopardising yield potential.

Of note, and not surprisingly, the greater the legume growth in the crop preceding wheat, the greater the potential to offset the requirement for applied nitrogen fertiliser. Other than poor crop growth, other factors that can reduce how much soil mineral nitrogen is fixed include low rainfall post-harvest resulting in residue not breaking down, mineralised nitrogen uptake by weeds between crops and other losses from erosion, leaching or gaseous emissions.

A final note

To fix nitrogen requires the inoculation of the legume with an appropriate strain of rhizobia such that nitrogen-fixing root nodules form. A survey of 225 pasture paddocks in NSW found that 93% had inadequate legume nodulation (Hackney et al., 2019) due to a combination of acidity (not typically an issue in the cropping regions of northern NSW or Queensland) and nutrient deficiencies, particularly of phosphorus and sulfur. These results highlight that to maximise the potential for legumes to fix nitrogen requires addressing underlying soil constraints and legume nutrient requirements. The GRDC Inoculating Legumes Practice and Science Manual is a handy reference for managing legumes.

Link to the paper

Don't miss out

If you don’t want to miss news, analysis and our content sharing research to help you become more drought resilient and innovative, you should subscribe and follow!

References

Farquharson, E.A., Ballard, R.A., Herridge DF, Ryder MH, Denton, M.D., Webster, A., Yates, R.J., Seymour, N.P., Deaker, R.J., Hartley, E., Gemmel, L.G., Hackney, B., O’Hara, G.W. 2022. Inoculating Legumes: Practice and Science, Grains Research and Development Corporation, Australia.

Gourley, H. & Kraak, J. 2024. An Australian assessment of nitrogen fertilizer inputs, efficiencies and gaseous losses. 2024 Australian Agronomy Conference.

Hackney, B., Jenkins, J., Powells, J., Edwards, C., De Meyer, S., Howieson, J. G., Yates, R. J. & Orgill, S. 2019. Soil acidity and nutrient deficiency cause poor legume nodulation in the permanent pasture and mixed farming zones of south-eastern Australia. Crop & Pasture Science, 70, 1128-1140.

Peoples, M. B., Li, X., Kirkegaard, J. A., Armstrong, R. D., Ciampitti, I. A., Franke, A. C., Giller, K. E., Hunt, J. R., Jeuffroy, M.-H. & Ladha, J. K et al. 2026. Integrating legumes to enhance cereal production: The relative inputs of fertiliser nitrogen and legume biological nitrogen fixation in major wheat and maize producing countries. Plant and Soil, 1-47.

Peoples, M. B., Kirkegaard, J. A., Li, X., Swan, J., Hunt, J. R., Herridge, D. 2026. Legumes in Australian farming systems and prospects to reduce the reliance on N fertiliser by diversifying wheat-based cropping systems with legumes. GRDC Update Papers, February 2026.

Perdman Chemicals and Fertilisers. Ceres, Perdman Chemicals and Fertilisers. https://perdamanchemicalsandfertilisers.com/project/ceres/

Whitelaw, A. 2026. Australia’s Urea Supply Is Now a Race Against the Clock. https://episode3.net. Published: 18 March 2026.

 

Posted: 14 April 2026